It is known that 6-fluoro-1-methylamino-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid derivatives of the Formula I ##STR5## (wherein R stands for piperazinyl or 4-methyl-piperazinyl) have outstanding antibacterial effects (Journal of Medicinal Chemistry 1984, 27, 1103; Antimicrobal Agents and Chemotherapy 1984, 25, 377; 1984, 26, 104; 275; 421; 781; 933; 1985, 27, 4 and 499; European Journal of Clinical Microbiology 1984, 3, 344; Clin. Therapy 1984, 7, 73).
The said compounds can be prepared by reacting 6-fluoro-7-chloro-1-methylamino-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid with a cyclic amine in pyridine or methoxyethanol, at the boiling point, under a protecting nitrogen atmosphere for 15-22 hours (European patent specification No. 90, 424; Japanese patent specification No. 84 01,468; Journal of Medicianl Chemistry 25, 377, 1984).